Did R. Feynman know about the different notations for exact and inexact differentials? [closed]

Question

I remember reading a long time ago, the story of a student taking R. Feynman for responsible of her (I think it was a woman, not sure though) fail at an exam of physics because what was written in her textbook was false and him to tell her back that she should have checked with other textbooks. In other words, it's not because you are R. Feynman that typos are impossible.

---

Recently, I read for the first time the chapters on thermodynamics and after all corrections that may have been done I am still surprised to read equations written as follow:

$$dQ + dW = dU \tag 1$$

$$ \Delta U = \Delta Q + \Delta W \tag 2$$

reference (09/18/2019)

---

Is that a pure error from himself, who, as little as I know him through his lectures, was really precise on details, or was the notations $\delta Q$ and $\delta W$ later introduced to clearly make the distinction between exact and inexact differentials?

Answer 1

There is no standardization for the notation of exact versus inexact differentials. In fact, I do not think I have ever seen the $\delta Q$ notation that you seemed to be expecting. Many authors have tried to introduce specific notations, but none of them has been uniformly adopted, and plenty of writers (such as Feynman) continue to write $dQ$, even though they know that $Q$ is not a state function. Moreover, other notations for inexact (some authors prefer "non-exact") differentials include $d\!\!\!\!\!\not\,Q$, and $\dot{Q}\,dt$. The last one, with $\dot{Q}$, seems to me to be potentially even more confusing than bare $dQ$, but it nonetheless gets a fair amount of use, particularly by engineers.